Macroscopic Quantum Tunneling of a Bose Condensate

TL;DR

This paper investigates the stability and decay mechanisms of a Bose-Einstein condensate with negative scattering length, highlighting metastability near critical temperature and calculating decay rates due to quantum and thermal fluctuations.

Contribution

It introduces a variational method to analyze condensate stability and accurately accounts for phase fluctuations, providing new insights into decay processes.

Findings

Condensate is generally unstable but becomes metastable near the critical temperature.

Decay rates due to macroscopic quantum fluctuations are calculated using WKB approximation.

Thermal fluctuation decay rates are also determined when relevant.

Abstract

We study, by means of a variational method, the stability of a condensate in a magnetically trapped atomic Bose gas with a negative scattering length and find that the condensate is unstable in general. However, for temperatures sufficiently close to the critical temperature the condensate turns out to be metastable. For that case we determine in the usual WKB approximation the decay rate of the condensate due to macroscopic quantum fluctuations. When appropriate, we also calculate the decay rate due to thermal fluctuations. An important feature of our approach is that (nonsingular) phase fluctuations of the condensate are taken into account exactly.